DDR4 not expected until 2015

Should start in excess of 2.1GHz

DDR3 MEMORY ALREADY has three years on its neck and it’s finally starting to replace DDR2 as the mainstream memory technology. JEDEC and the memory manufacturers are already planning the next generation of memory technology set to succeed DDR3 with the obvious name of DDR4 which was set to make its first appearance in 2012, but it seems like things have been pushed back until 2015 now.

Impress posted some coverage from MemCon Tokyo 2010 with roadmaps showing DDR4 having been pushed back to 2015, as it isn’t considered realistic to replace DDR3 any sooner. As a result of pushing back DDR4 memory, we’ll be seeing faster DDR3 memory which will be part of the JEDEC standard. Sadly this also means higher latencies in the future; at least unless JEDEC changes its current plans where DDR3 2133MHz modules will have default timings of 12-12-12 compared to 8-8-8 or 9-9-9 at which most DDR3 1333MHz modules are rated at today.

The current plans for DDR4 memory will bring some changes as to how the system memory is being accessed, as DDR3 memory is connected in pairs to the memory controller while DDR4 will use a point to point interface with only one DIMM per channel. This won’t have a huge impact on desktop systems and notebooks, but for servers and workstations this could cause some issues. However, one of the solutions includes using a memory switch which can support multiple DIMMs per memory controller and it allows for a simpler motherboard layout. This should see servers and high-end workstations being able to accept far more memory than what’s possible today.

The other option is to use FB-DIMM’s just as for DDR3, but this is a much more costly solution than using a switch on the memory bus. There’s also some work being done on layering the actual DRAM chips on top of each other to produce higher density DIMMs which would be another solution around the problem. This would be the most cost efficient solution and stacks of four to eight DRAM chips are being considered. As this is all still work in progress, we’ll have to wait and see which solution becomes the winner in the end.

The current roadmaps are pointing at a starting frequency of 2133MHz for DDR4 DIMMs, although some high-end DDR3 memory is already available at these speeds and even faster. The roadmap outlines speeds of up to 4266MHz, although this is in the long term plans which are unlikely to be met until close to 2020. Once again we’ll see lower Voltage modules with a suggested initial 1.2V, but 1.1 or 1.05V might become the final spec. However, lowering the Voltage isn’t going to be easy with the kind of speeds that are being discussed, at least not with today’s manufacturing processes. The DRAM industry is getting ready to move on to 2xnm technology by 2013 or so, which should help to solve most of the current problems.

There doesn’t seem to be any big technology advances, unlike GDDR5 which uses a quad pumped bus to boost the performance. As such it won’t offer any huge performance benefits clock for clock compared to DDR3, just as DDR3 didn’t offer any huge performance advantages over DDR2 at the same clock speed. But as always it’s the industry that’s pushing for new standards and the world doesn’t stand still, so once Intel and friends decides it’s time to move on to something newer and faster, the industry will shift its focus from the old towards the new.S|A

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Charlie Demerjian is the founder of Stone Arch Networking Services and S|A. SemiAccurate.com is a technology news site; addressing hardware design, software selection, customization, security and maintenance, with over one million views per month. He is a technologist and analyst specializing in semiconductors, system and network architecture.

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